INTERNAL STRUCTURE OF THE GRASSHOPPER. 261 



FIG. 139. Female specimen of Acridium Americanum, dissected to 

 show the digestive and reproductive organs, and the ventral nerve-chain. 

 (Drawn from nature by W. K. Brooks). 



a. Antenna, a 1 , a-, a :! , a 4 , a 5 , the abdominal ganglia, b. Tooth car- 

 ried by the prosternum. c. Compound eye. d. Epicranium. e. Cly- 

 peus. /. Femur, fu. Furcula. <j. Labrum. ig. Ingluvies. il. Ilium. 

 in. Maxillary palpus, n. Labial palpus, o. Ovary, p. Podical plate. 

 (H>. Gastric coeca. mj>. Malpighian tubules. r. Rectum. s. Sper- 

 matheca. sa. Salivary glands. s<j. Gastric ganglia. t. Tibia. 

 t 2 , t 3 . Second and third thoracic ganglia, ty. Tegmen. tr. Tarsus. 

 op, op', op' 1 . Ovipositor, vn. Ventriculus. w. Whig. 1'. Prothoracic 

 prescutum. 1". Prothoracic scutum. 1'". Prothoracic scutellum. 

 1. Prothoracic postscutellum. 2. Mesothoracic tergum. 3. Metatho- 

 racic tergum. ^-13. The ten abdominal terga. 1*-11*. The thoracic and 

 abdominal sterna. 



and vary slightly in structure according to the genus. 

 The folio wing description is strictly true only of the genus 

 Acridium. In order to expose these organs, dissect away 

 the corpus adiposum, the wing muscles, and the dorsal 

 integument of the head. 

 They consist of : 



1. The oesophagus, a tough, dark-brown, cylindrical 

 tube, which runs up from the mouth, and then bends at 

 right angles and pusses into the thorax. 



2. In the mesothorax the oesophagus gradually enlarges 

 to form ;i thick-walled pouch, the ingluvies or crop (Fig. 

 131), iy), which occupies the mesothoracic and metatho- 

 racic segments. 



3. On the sides of the anterior end of the ingluvies are 

 the delicate, white, dendritic, salivary glands (Fig. 129, sa) 

 which communicate with two salivary ducts, one of which 

 runs forward on each side of the oesophagus into the head, 

 where they open into the cavity of the mouth. 



4. In many insects the ingluvies is sharply separated by 

 a constriction from the next region or proventriculus, but 

 there is no abrupt division in Acridium, and the proven- 



